Pyrotechnic devices and firing mechanisms for aircraft canopy jettison

ABSTRACT

Pyrotechnic devices and firing mechanisms for aircraft canopy jettison are disclosed herein. An example firing mechanism includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a primary charge disposed in the second bore, a closure disc between the second bore and the channel, and a firing pin assembly disposed in the first bore. The firing pin assembly includes a percussion primer and a firing pin piston including a piston body, a firing pin extending from the piston body, and a piercing pin extending from the piston body. In response to a firing signal, the firing pin piston is moved toward the primary charge such that the piercing pin punctures the closure disc and the firing pin engages the percussion primer to ignite the primary charge.

GOVERNMENT LICENSE RIGHTS

This invention was made with Government support under 18-D-0107 awardedby the United States Department of Defense. The government has certainrights in this invention.

FIELD OF THE DISCLOSURE

This disclosure relates generally to aircraft and, more particularly, topyrotechnic devices and firing mechanisms for aircraft canopy jettison.

BACKGROUND

Some known aircraft include an ejection system for ejecting a seat(along with a pilot) from a cockpit of the aircraft. Prior to ejectingthe seat (along with the pilot), a canopy over the cockpit is jettisonedfrom the aircraft so that the seat (and/or the pilot) do not collidewith the canopy during ejection. The aircraft includes athrusting/unlatching system that quickly unlatches the canopy prior toinitiating the launching of the canopy from the fuselage. Thisthrusting/unlatching system includes one or more pyrotechnic devicesthat provide fast, powerful actuations.

SUMMARY

An example firing mechanism for a pyrotechnic device disclosed hereinincludes a housing defining a first bore, a second bore, and a channelbetween the first bore and the second bore, a primary charge disposed inthe second bore, a closure disc between the second bore and the channel,and a firing pin assembly disposed in the first bore. The firing pinassembly includes a percussion primer and a firing pin piston includinga piston body, a firing pin extending from the piston body, and apiercing pin extending from the piston body. In response to a firingsignal, the firing pin piston is moved toward the primary charge suchthat the piercing pin punctures the closure disc and the firing pinengages the percussion primer to ignite the primary charge.

An example pyrotechnic device disclosed herein includes a body defininga chamber, a piston disposed in the chamber, and a firing mechanismcoupled to the body. The firing mechanism is to, when triggered,generate high pressure in the chamber to move the piston. The firingmechanism includes a housing defining a first bore, a second bore, and achannel between the first bore and the second bore, a firing pinassembly disposed in the first bore, a primary charge disposed in thesecond bore, and first and second closure discs welded to the housing tohermetically seal the primary charge in the second bore.

An example aircraft disclosed herein includes a forward fuselagedefining a cockpit, a canopy removably coupled to the forward fuselageover the cockpit, and a pyrotechnic device to unlatch the canopy fromthe forward fuselage. The pyrotechnic device includes a firingmechanism. The firing mechanism includes a housing defining a firstbore, a second bore, and a channel between the first bore and the secondbore, a primary charge disposed in the second bore, a closure discbetween the second bore and the channel, a percussion primer, and afiring pin piston including a piston body, a firing pin extending fromthe piston body, and a piercing pin extending from the piston body. Thefiring pin is a first distance from the percussion primer and thepiercing pin is a second distance from the closure disc. The seconddistance being less than the first distance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example aircraft in which the examples disclosedherein can be implemented.

FIG. 2 is a cross-sectional view of an example pyrotechnic deviceincluding an example firing mechanism that can be implemented on theaircraft of FIG. 1 .

FIG. 3 is an enlarged cross-sectional view of the example firingmechanism of FIG. 2 .

FIGS. 4A-4C show an example sequence of firing the example firingmechanism of FIGS. 2 and 3 .

The figures are not to scale. In general, the same reference numberswill be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts.

Descriptors “first,” “second,” “third,” etc. are used herein whenidentifying multiple elements or components which may be referred toseparately. Unless otherwise specified or understood based on theircontext of use, such descriptors are not intended to impute any meaningof priority, physical order or arrangement in a list, or ordering intime but are merely used as labels for referring to multiple elements orcomponents separately for ease of understanding the disclosed examples.In some examples, the descriptor “first” may be used to refer to anelement in the detailed description, while the same element may bereferred to in a claim with a different descriptor such as “second” or“third.” In such instances, it should be understood that suchdescriptors are used merely for ease of referencing multiple elements orcomponents.

DETAILED DESCRIPTION

Disclosed herein are example firing mechanisms and example pyrotechnicdevices incorporating such example firing mechanisms. The examplepyrotechnic devices and firing mechanisms disclosed can be used on anaircraft canopy jettison system, for example. The example firingmechanisms disclosed herein have longer lifespans than known firingmechanisms, which reduces costs and maintenance associated withreplacing and/or servicing the firing mechanisms.

Pyrotechnic devices are used in many applications. In general,pyrotechnic devices convert a small explosive or combustive force into aworking force that can be used to move one or more objects. For example,some aircraft, such as fighter planes, include an ejection system thatcan be triggered to eject one or more pilots from a cockpit of theaircraft. Before ejecting the pilot(s), a canopy over the cockpit isjettisoned (removed) from the cockpit according to a jettison sequence.The canopy jettison system includes one or more pyrotechnic devices(e.g., a series of pyrotechnic devices). The pyrotechnic device(s), whentriggered, can be used to provide a fast, powerful burst of motion tohelp unlock and/or launch canopy away from the fuselage.

Example pyrotechnic devices disclosed herein include a firing mechanism.The firing mechanism includes a primary charge (e.g., propellant) and apiston or firing pin assembly that can ignite the primary charge. Theprimary charge, when activated (e.g., ignited), provides a high pressureburst that is used to generate motion or working power. The primarycharge material tends to deteriorate when exposed to atmosphericconditions. Therefore, known firing mechanisms attempt to seal theprimary charge between two discs constructed of Mica, which is brittleenough to be ruptured during the ignition process. However, these knowndiscs still allow leak paths to the atmosphere. Therefore, known firingmechanism devices have limited lifespans (e.g., only a few years) andmust be removed, discarded, and replaced periodically. This lifespan canbe shortened even further because of the harsh atmospheric conditionsexperienced during flight.

Disclosed herein are example firing mechanisms that include weldedclosure discs to seal the primary charge. In particular, the closurediscs, which are constructed of metal (e.g., stainless steel), arewelded to the housing of the firing mechanism. This enables the primarycharge to be hermetically sealed in the body of the firing mechanism,thereby preventing or substantially limiting leak paths to the primarycharge. As such, the example firing mechanisms have longer lifespansthan known firing mechanisms.

The example firing mechanisms disclosed herein include a firing pinpiston with a piercing pin that is used to puncture one of the weldedclosure discs during activation. This ensures the welded closure disc isruptured or opened. This also eliminates the need for an ignitioncharge, which is commonly used in known firing mechanisms between thepercussion primers and the primary charge. For example, when a firingsignal is received (e.g., during a canopy jettison operation), thefiring pin piston is moved toward the welded closed disc such that thepiercing pin engages and punctures a hole in the welded closure disc.Further, the firing pin piston includes one or more firing pins thatimpacts one or more percussion primers, which creates a spark or hotbyproducts that ignite the primary charge. In some examples, thedistance between the piercing pin and the closure disc is less than thedistance between the firing pin(s) and the percussion primer(s). Assuch, when the firing pin piston is fired, the piercing pin punctures ahole in the welded closure disc first, and then the percussion primer(s)are activated. This ensures there is a flow path for the spark or hotbyproducts from the percussion primer(s) to ignite the primary charge.

Now turning to the figures, FIG. 1 illustrates an example aircraft 100in which the examples disclosed herein can be implemented. In theillustrated example, the aircraft 100 includes a fuselage 102, wings104, horizontal stabilizers 106, vertical stabilizers 108, and engines110 (e.g., jet engines). In operation, the engines 110 generate thrustto propel the aircraft 100 forward while the wings 104 generate lift.The wings 104, the horizontal stabilizers 106, and/or the verticalstabilizers 108 can include movable control surfaces (e.g., ailerons,flaps, elevators, rudders, etc.) to maneuver the aircraft 100 whilethrust is provided by the engines 110. In other examples, the aircraft100 can include more or fewer engines and/or more or fewer flightcontrol surfaces.

In the illustrated example, the aircraft 100 includes a forward fuselage112 (sometimes referred to as an aircraft forebody). The forwardfuselage 112 defines a cockpit 114. One or more persons (e.g., a pilot,a passenger, etc.) can sit in the cockpit 114 to operate and/orotherwise travel in the aircraft 100. In this example, the cockpit 114holds two persons. In other examples, the cockpit 114 may be designed tohold only one person or more than two persons. The person(s) sit inrespective seats in the cockpit 114.

In the illustrated example, the aircraft 100 includes a canopy 116disposed over the cockpit 114. The canopy 116 is at least partiallyconstructed of transparent glass, plastic, or other material thatenables the pilot(s) and/or passenger(s) to see out of the aircraft 100.The canopy 116 is removably coupled to the forward fuselage 112 over thecockpit 114 and can be removed from the forward fuselage 112 during anejection operation or sequence. In particular, the aircraft 100 includesan ejection system that can be used to eject the seat(s) from theaircraft 100 during a critical situation. Prior to ejecting the seat(s),the example ejection system jettisons the canopy 116 from the forwardfuselage 112. The example ejection system includes one or morepyrotechnic devices to jettison the canopy 116 away from the forwardfuselage 112. In particular, the pyrotechnic device(s) provide fast,powerful actuating means to unlatch and launch the canopy 116 away fromthe forward fuselage 112. For example, the ejection system can include acanopy unlatch thruster and one or more rocker motors. The unlatchthruster, when activated, actuates a series of mechanisms to unlatch thecanopy 116 from the forward fuselage 112. Then, the rocket motors propelor launch the canopy 116 upward. The canopy unlatch thruster and/or therocket motor can include and/or be activated by one or more pyrotechnicdevices. Therefore, the example pyrotechnic devices disclosed herein canbe used to unlatch the canopy 116 from the forward fuselage 112 prior toinitiating the jettisoning of the canopy 116 away from the forwardfuselage 112. Example pyrotechnic devices are disclosed in furtherdetail here.

In the illustrated example, the aircraft 100 is depicted as a type offighter jet aircraft. However, the example pyrotechnic devices andfiring mechanisms disclosed herein can be implemented in any other typeof vehicle, such as other fixed wing aircraft (e.g., a commercialaircraft), non-fixed wing aircraft, and/or other types of vehicles(e.g., a car, a train, etc.). Further, the example pyrotechnic devicesand firing mechanisms disclosed herein can be implemented innon-vehicular applications.

FIG. 2 is a cross-sectional view of an example pyrotechnic device 200including an example firing mechanism 202 constructed in accordance withteachings of this disclosure. The pyrotechnic device 200 can also bereferred to as a gas generator pyrotechnic device. The pyrotechnicdevice 200, when activated or triggered, is used to move a workingdevice. For example, the pyrotechnic device 200 can be part of theejection system and used to unlock and/or launch the canopy 116 (FIG. 1).

In the illustrated example, the pyrotechnic device 200 includes a body204. In this example, the body 204 includes a first body portion 206coupled to a second body portion 208 via a collar 210 (e.g., a threadedcollar). The first body portion 206 can be considered a manifold, andthe second body portion 208 can be considered an actuator cylinder. Inother examples, the body 204 can include more or fewer body portions.The second body portion 208 of the body 204 defines a chamber 212. Inthe illustrated example, the pyrotechnic device 200 includes a piston214 disposed in the chamber 212, and a stem 216 coupled to the piston214 and extending outward from the second body portion 208. The stem 216can be coupled to another structure or system used to unlock and/orlaunch the canopy 116 (FIG. 1 ).

In the illustrated example, the firing mechanism 202 is coupled to anddisposed in the body 204. In particular, in this example, the firingmechanism 202 is partially disposed in each of the first body portion206 and the second body portion 208. In the illustrated example, awasher or spacer 215 is disposed above the firing mechanism 202 in thesecond body portion 206. The firing mechanism 202 is clamped between thefirst body portion 206 and the second body portion 208. Additionally oralternatively, in some examples the firing mechanism 202 is held in thebody 204 via welding and/or threaded fastener(s). In the illustratedexample, the pyrotechnic device 200 includes one or more seals 217(e.g., o-rings) between the body 204 and the firing mechanism 202. Theseals 217 prevent or limit gas or other fluid from leaking past thefiring mechanism 202. The first body portion 206 defines a passageway218 to the firing mechanism 202. To activate the pyrotechnic device 200,a firing signal is supplied to the passageway 218. The firing signal canbe a pressure signal (e.g., a burst of high pressure air). The firingsignal activates or triggers the firing mechanism 202. The firingmechanism 202 ignites a charge or propellant, which provides a highpressure pulse or burst into the chamber 212. This high pressure movesthe piston 214 and, thus, the stem 216. As mentioned above, the stem 216can be coupled to one or more structures or systems for unlocking and/orlaunching the canopy 116 (FIG. 1 ). Therefore, when the firing mechanism202 is triggered and the piston 214 is moved, the canopy 116 is unlockedand/or launched.

FIG. 3 is an enlarged cross-sectional view of the firing mechanism 202.The firing mechanism 202 includes a body or housing 300 (which may alsobe referred to as a booster housing) having a first end 302 and a secondend 304 opposite the first end 302. The housing 300 defines a first bore306 extending into the first end 302, a second bore 308 extending intothe second end 304, and a channel 310 between the first bore 306 and thesecond bore 308. Therefore, the first and second bores 306, 308 and thechannel 310 form a passageway or channel 312 between extending betweenthe first and second ends 302, 304. In some examples, the housing 300 isconstructed of metal, such as stainless steel. Additionally oralternatively, the housing 300 can be constructed of other materials(e.g., aluminum).

In the illustrated example, the firing mechanism 202 includes a primarycharge 314 (which can also be referred to as a primary propellantcharge) disposed in the second bore 308. In some examples, the primarycharge 314 includes titanium hydride potassium perchlorate (THPP). Inother examples, the primary charge 314 can include other materials, suchas zirconium potassium perchlorate (ZPP). The primary charge 314 can beinstalled or inserted into the second bore 308 from the second end 304.To prevent air from leaking into the second bore 308 and potentiallydeteriorating the primary charge 314, the primary charge 314 ishermetically sealed in the second bore 308. In the illustrated example,the firing mechanism 202 includes a first closure disc 316 coupled tothe housing 300 between the second bore 308 and the channel 310 and asecond closure disc 318 coupled to the second end 304 over the secondbore 308. The first and second closure discs 316, 318 are constructed ofmetal, such as stainless steel. In this example, the first and secondclosure discs 316, 318 are welded to the housing 300. For example, thefirst closure disc 316 can be welded to an inner surface 320 of thehousing 300 between the second bore 308 and the channel 310 (e.g., at ashoulder between the second bore 308 and the channel 310) and the secondclosure disc 318 can be welded to the second end 304 over the secondbore 308. As such, the primary charge 314 is hermetically sealed betweenthe first and second closure discs 316, 318 in the second bore 308. Thislimits and/or prevents atmospheric air from leaking into the second bore308 and potentially deteriorating the primary charge 314. As such, theprimary charge 314 has a longer life span or shelf life.

In the illustrated example, the firing mechanism 202 includes a firingpin assembly 322 disposed in the first bore 306. The firing pin assembly322 can be installed or inserted in the first bore 306 from the firstend 302. The firing pin assembly 322 is used to ignite or activate theprimary charge 314, as disclosed in further detail herein. The firingpin assembly 322 includes a body or housing 324 having a first end 326and a second end 328 opposite the first end 326. In some examples, thehousing 324 of the firing pin assembly 322 is held in the housing 300via the washer 215 (FIG. 2 ), which is retained by the first bodyportion 206 (FIG. 2 ). In the illustrated example, the firing mechanism202 includes a seal 330 between the housing 324 of the firing pinassembly 322 and the housing 300 of the firing mechanism 202. The seal330 limits or prevents air leakage between the housings 300, 324 (beforefiring) and also limits or prevents leakage of combustion gasses afterthe primary charge 314 is initiated.

In the illustrated example, the firing pin assembly 322 includes afiring pin piston 332 disposed in the housing 324. The firing pin piston332 includes a piston body 334 and a piercing pin 336 coupled to andextending downward from the piston body 334. In this example, thepiercing pin 336 is threadably coupled to the piston body 334. In someexamples, this allows for easy assembly, positioning, and installation.In other examples, the piercing pin 336 can be coupled to the pistonbody 334 via other techniques (e.g., welding, fasteners, etc.). In stillother examples, the piercing pin 336 and the piston body 334 can beformed as a single unitary part or component (e.g., a monolithicstructure). In some examples, the piercing pin 336 is constructed ofmetal, such as steel. In the illustrated example, the housing 324 of thefiring pin assembly 322 defines an upper channel 338 in the first end326. The piston body 334 is disposed in and moveable (e.g., slidable) upand down in the upper channel 338. In the illustrated example, one ormore seals 340 (e.g., o-rings) are disposed between the piston body 334and the housing 324.

In the illustrated example of FIG. 3 , the housing 324 of the firing pinassembly 322 also defines a central pin channel 342 between the upperchannel 338 and the second end 328. The piercing pin 336 is disposed inand moveable (e.g., slidable) in the central pin channel 342. Thehousing 324 of the firing pin assembly 322 defines a first lower channel344 and a second lower channel 346 that extend between the upper channel338 and the second end 328. In the illustrated example, the firing pinpiston 332 includes a first firing pin 348 that extends from the pistonbody 334 into the first lower channel 344 and a second firing pin 350that extends from the piston body 334 into the second lower channel 346.In the illustrated example, the firing pin assembly 322 includes a firstpercussion primer 352 disposed in the first lower channel 344 and asecond percussion primer 354 disposed in the second lower channel 346.The central pin channel 342 is parallel to and between the first andsecond lower channels 344, 346. While in this example the firing pinassembly 322 includes two lower channels and two percussion primers, inother examples, the firing pin assembly 322 may only include one lowerchannel and one percussion primer.

In an example firing sequence, a pressurized signal is received on thetop of the firing pin piston 332. This creates a force the moves thefiring pin piston 332 downward in FIG. 3 toward the primary charge 314.As the firing pin piston 332 moves downward toward the primary charge314, the piercing pin 336 punctures or pierces the first closure disc316. This creates a hole or opening in the first closure disc 316. Atthe same time or after, the first and second firing pins 348, 350 of thefiring pin piston 332 engage or impact the first and second percussionprimers 352, 354. The percussion primers 352, 354 activate (e.g., burst)to emit hot byproducts and/or a spark. The hot byproducts and/or sparktravels through the channel 310 and through the hole created in thefirst closure disc 316 to the primary charge 314. The primary charge 314activates (e.g., ignites) and ruptures the second closure disc 318.Therefore, in response to a firing signal, the firing pin piston 332 ismoved toward the primary charge 314 such that the piercing pin 336punctures the first closure disc 316 and the first firing pin 348engages the first percussion primer 352 to ignite the primary charge314. The high pressure ignition byproducts from the primary charge 314fill the chamber 212 (FIG. 2 ) of the pyrotechnic device 200 (FIG. 2 ),which moves the piston 214 (FIG. 2 ).

Because the piercing pin 336 pierces or punctures the first closure disc316 to provide a path for the ignition products, the example firingmechanism 202 does not include an ignition charge between the percussionprimers 352, 354 and the primary charge 314 as seen in known firingmechanisms. Such ignition charges are not retained in their ownenclosures and therefore limit the life of the firing mechanism.Therefore, in the example firing mechanism 202, all propellant materialin the firing mechanism 202 is hermetically sealed or protected by thewelded enclosure. This significantly increases the life span or shelflife of the example firing mechanism 202 compared to known firingmechanisms. This also reduces costs and weight associated with thefiring mechanism 202.

In the illustrated example of FIG. 3 , the firing mechanism 202 includesa shear pin 356 that extends through the housing 324 and the firing pinpiston 332. The shear pin 356 holds the firing pin piston 332 in placeuntil a sufficient force from a pressurized firing signal is created onthe firing pin piston 332. This prevents the firing pin piston 322 frompre-maturely moving in the housing 324 and accidently igniting theprimary charge 314. When a sufficient force is created on the firing pinpiston 332 from the pressurized firing signal, this force causes theshear pin 356 to break, which allows the firing pin piston 332 to movedownward in the housing 324. Therefore, the firing pin piston 332 has acertain surface area (e.g., on the top side) on which the pressurizedfiring signal operates to (1) break the shear pin 356 and (2) move thefiring pin piston 332 downward with enough force to puncture the firstclosure disc 316. In some examples, the pressurized firing signal isabout at least 450 pounds-per-square-inch (psi). In other examples, thepressurized firing signal may be greater than or less than 450 psi.

In the illustrated example, the distal ends of the first and secondfiring pins 348, 350 have semi-circular nubs or protrusions 358, 360. Insome examples, this shape results in an increased impact force per unitarea (by reducing the area of contact) of the firing pin piston 332 onthe percussion primers 352, 354. In other examples, the distal ends ofthe first and second firing pins 348, 350 may have another shape or maybe flat.

In the illustrated example, the piercing pin 336 has a barbed tip or end362. The barbed tip 362 is formed by a shaft 364 with a conical orpointed tip 366. The widest part of the conical tip 366 is wider thanthe shaft 364. As such, when the conical tip 366 punctures the firstclosure disc 316, the conical tip 366 creates an opening that is largerthan the shaft 364. This creates a flow path between the shaft 364 andthe first closure disc 316 for the spark from the percussion primers352, 354 to reach the primary charge 314.

As shown in FIG. 3 , when the firing pin piston 332 is in the pre-firedposition, the first firing pin 348 is spaced from the first percussionprimer 352 by a first distance of D1. The second firing pin 350 issimilarly spaced from the second percussion primer 354 by the firstdistance of D1. Further, the piercing pin 336 (e.g., the barbed tip 362of the piercing pin 336) is spaced from the first closure disc 316 by asecond distance of D2. The second distance D2 is less than the firstdistance D1. Therefore, when the firing pin piston 332 is moved towardthe primary charge 314 (e.g., downward in FIG. 3 ), the piercing pin 336engages or punctures the first closure disc 316 before the first andsecond firing pins 348, 350 engage the percussion primers 352, 354. Thisenables the piercing pin 336 to puncture the first closure disc 316before the percussion primers 352, 354 are ignited. Therefore, when thepercussion primers 352, 354 are triggered, the spark can travel to theprimary charge 314.

FIGS. 4A-4C illustrate an example sequence of firing the firingmechanism 202 in the pyrotechnic device 200. Each of FIGS. 4A-4C shows aperspective cross-sectional view of the pyrotechnic device 200 and thefiring mechanism 202 and an enlarged callout of the first closure disc316 of the firing mechanism 202.

FIG. 4A shows the firing pin piston 332 in the pre-fired position. Theshear pin 356 is intact, which holds the firing pin piston 332 in thisposition until a firing signal is received. As shown in the callout ofFIG. 4A, the piercing pin 336 is spaced apart from the first closuredisc 316.

As shown in FIG. 4B, when a firing signal is received, the pressure inthe passageway 218 of the first body portion 206 creates a force on thefiring pin piston 332. The force on the firing pin piston 332 causes theshear pin 356 to break. As the firing pin piston 332 moves downward, thebarbed tip 362 of the piercing pin 336 engages the first closure disc316. This punctures a hole or opening in the first closure disc 316.

As shown in FIG. 4C, the firing pin piston 332 continues to movedownward until the first and second firing pins 348, 350 of the firingpin piston 332 impact the first and second percussion primers 352, 354.When the first and second percussion primers 352, 354 are impacted bythe first and second firing pins 348, 350, the first and secondpercussion primers 352, 354 activate. This creates a hot spark and/orhot byproducts that travel downward to the primary charge 314. As shownin the callout in FIG. 4C, the barbed tip 362 has passed through thefirst closure disc 316, which creates an opening 400. The opening islarger than the shaft 364, which forms a forms a flow path for the hotspark or byproducts. The hot spark or byproducts ignite the primarycharge 314. The primary charge 314 ruptures the second closure disc 318(FIG. 3 ), which creates a high pressure burst in the chamber of thepyrotechnic device 200.

From the foregoing, it will be appreciated that example apparatus havebeen disclosed that improve sealing of a primary propellant charge in afiring mechanism of a pyrotechnic device. This improved sealingsignificantly increases the lifespan of the firing mechanism, therebyreducing costs associated with maintenance and replacement of the firingmechanism. Examples disclosed herein also provide an improved manner forpuncturing a closure disc to ensure the primary charge is ignited.

Example methods, apparatus, systems, and articles of manufacture aredisclosed herein. Further examples and combinations thereof include thefollowing:

Example 1 is a firing mechanism for a pyrotechnic device. The firingmechanism comprises a housing defining a first bore, a second bore, anda channel between the first bore and the second bore, a primary chargedisposed in the second bore, a closure disc between the second bore andthe channel, and a firing pin assembly disposed in the first bore. Thefiring pin assembly includes a percussion primer and a firing pin pistonincluding a piston body, a firing pin extending from the piston body,and a piercing pin extending from the piston body. In response to afiring signal, the firing pin piston is moved toward the primary chargesuch that the piercing pin punctures the closure disc and the firing pinengages the percussion primer to ignite the primary charge.

Example 2 includes the firing mechanism of Example 1, wherein theclosure disc is welded to the housing.

Example 3 includes the firing mechanism of Example 2, wherein theclosure disc is a first closure disc, the firing mechanism furtherincluding a second closure disc welded to the housing such that theprimary charge is hermetically sealed between the first and secondclosure discs.

Example 4 includes the firing mechanism of any of Examples 1-3, whereinthe closure disc is constructed of metal.

Example 5 includes the firing mechanism of any of Examples 1-4, wherein,when the firing pin piston is in a pre-fired position, the firing pin isa first distance from the percussion primer and the piercing pin is asecond distance from the first closure disc, the second distance beingless than the first distance, such that when the firing pin piston ismoved toward the primary charge, the piercing pin punctures the closuredisc before the firing pin engages the percussion primer.

Example 6 includes the firing mechanism of any of Examples 1-5, whereinthe piercing pin has a barbed tip.

Example 7 includes the firing mechanism of any of Examples 1-6, whereinthe piercing pin is threadably coupled to the piston body.

Example 8 includes the firing mechanism of any of Examples 1-7, whereinthe percussion primer is a first percussion primer and the firing pin isa first firing pin. The firing pin assembly further includes a secondpercussion primer. The firing pin piston has a second firing pinextending from the piston body, such that when the firing pin piston ismoved toward the primary charge the second firing pin engages the secondpercussion primer.

Example 9 includes the firing mechanism of Example 8, wherein thehousing defines a first lower channel, a second lower channel, and acentral pin channel. The first percussion primer is disposed in thefirst lower channel, the second percussion primer is disposed in thesecond lower channel, and the piercing pin is disposed in the centralpin channel. The central pin channel is parallel to and between thefirst and second lower channels.

Example 10 includes the firing mechanism of any of Examples 1-9, whereinthe firing mechanism does not include an ignition charge between thepercussion primer and the primary charge.

Example 11 is a pyrotechnic device comprising a body defining a chamber,a piston disposed in the chamber, and a firing mechanism coupled to thebody. The firing mechanism is to, when triggered, generate high pressurein the chamber to move the piston. The firing mechanism includes ahousing defining a first bore, a second bore, and a channel between thefirst bore and the second bore, a firing pin assembly disposed in thefirst bore, a primary charge disposed in the second bore, and first andsecond closure discs welded to the housing to hermetically seal theprimary charge in the second bore.

Example 12 includes the pyrotechnic device of Example 11, wherein thefirst closure disc is welded to an inner surface of the housing definingthe second bore.

Example 13 includes the pyrotechnic device of Example 12, wherein thesecond closure disc is welded to an end of the housing over the secondbore.

Example 14 includes the pyrotechnic device of any of Examples 11-13,wherein the firing pin assembly includes a firing pin piston including apiercing pin to puncture the first closure disc when the firing pinpiston is moved toward the primary charge.

Example 15 includes the pyrotechnic device of Example 14, wherein thepiercing pin has a barbed tip.

Example 16 includes the pyrotechnic device of Examples 14 or 15, whereinthe firing pin piston includes a piston body, the piercing pin coupledto and extending from the piston body.

Example 17 includes the pyrotechnic device of Example 16, wherein thefiring pin assembly includes a percussion primer, and wherein the firingpin piston includes a firing pin extending from the piston body. Thefiring pin is to engage the percussion primer when the firing pin pistonis moved toward the primary charge.

Example 18 is an aircraft comprising a forward fuselage defining acockpit, a canopy removably coupled to the forward fuselage over thecockpit, and a pyrotechnic device to unlatch the canopy from the forwardfuselage. The pyrotechnic device includes a firing mechanism. The firingmechanism includes a housing defining a first bore, a second bore, and achannel between the first bore and the second bore, a primary chargedisposed in the second bore, a closure disc between the second bore andthe channel, a percussion primer, and a firing pin piston including apiston body, a firing pin extending from the piston body, and a piercingpin extending from the piston body. The firing pin is a first distancefrom the percussion primer and the piercing pin is a second distancefrom the closure disc. The second distance is less than the firstdistance.

Example 19 includes the aircraft of Example 18, wherein the closure discis welded to the housing.

Example 20 includes the aircraft of Examples 18 and 19, wherein thepiercing pin has a barbed tip.

“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim employs any formof “include” or “comprise” (e.g., comprises, includes, comprising,including, having, etc.) as a preamble or within a claim recitation ofany kind, it is to be understood that additional elements, terms, etc.may be present without falling outside the scope of the correspondingclaim or recitation. As used herein, when the phrase “at least” is usedas the transition term in, for example, a preamble of a claim, it isopen-ended in the same manner as the term “comprising” and “including”are open ended. The term “and/or” when used, for example, in a form suchas A, B, and/or C refers to any combination or subset of A, B, C such as(1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) Bwith C, and (7) A with B and with C. As used herein in the context ofdescribing structures, components, items, objects and/or things, thephrase “at least one of A and B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. Similarly, as used herein in the contextof describing structures, components, items, objects and/or things, thephrase “at least one of A or B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. As used herein in the context ofdescribing the performance or execution of processes, instructions,actions, activities and/or steps, the phrase “at least one of A and B”is intended to refer to implementations including any of (1) at leastone A, (2) at least one B, and (3) at least one A and at least one B.Similarly, as used herein in the context of describing the performanceor execution of processes, instructions, actions, activities and/orsteps, the phrase “at least one of A or B” is intended to refer toimplementations including any of (1) at least one A, (2) at least one B,and (3) at least one A and at least one B.

As used herein, singular references (e.g., “a”, “an”, “first”, “second”,etc.) do not exclude a plurality. The term “a” or “an” entity, as usedherein, refers to one or more of that entity. The terms “a” (or “an”),“one or more”, and “at least one” can be used interchangeably herein.Furthermore, although individually listed, a plurality of means,elements or method actions may be implemented by, e.g., a single unit orprocessor. Additionally, although individual features may be included indifferent examples or claims, these may possibly be combined, and theinclusion in different examples or claims does not imply that acombination of features is not feasible and/or advantageous.

Although certain example methods, apparatus, systems, and articles ofmanufacture have been disclosed herein, the scope of coverage of thispatent is not limited thereto. On the contrary, this patent covers allmethods, apparatus and articles of manufacture fairly falling within thescope of the claims of this patent.

The following claims are hereby incorporated into this DetailedDescription by this reference, with each claim standing on its own as aseparate embodiment of the present disclosure.

What is claimed is:
 1. A firing mechanism for a pyrotechnic device, thefiring mechanism comprising: a housing defining a first bore, a secondbore, and a channel between the first bore and the second bore; aprimary charge disposed in the second bore; a closure disc between thesecond bore and the channel; and a firing pin assembly disposed in thefirst bore, the firing pin assembly including: a percussion primer; anda firing pin piston including a piston body, a firing pin extending fromthe piston body, and a piercing pin extending from the piston body,wherein, in response to a firing signal, the firing pin piston is movedtoward the primary charge such that the piercing pin punctures theclosure disc and the firing pin engages the percussion primer to ignitethe primary charge.
 2. The firing mechanism of claim 1, wherein theclosure disc is welded to the housing.
 3. The firing mechanism of claim2, wherein the closure disc is a first closure disc, the firingmechanism further including a second closure disc welded to the housingsuch that the primary charge is hermetically sealed between the firstand second closure discs.
 4. The firing mechanism of claim 1, whereinthe closure disc is constructed of metal.
 5. The firing mechanism ofclaim 1, wherein, when the firing pin piston is in a pre-fired position,the firing pin is a first distance from the percussion primer and thepiercing pin is a second distance from the first closure disc, thesecond distance being less than the first distance, such that when thefiring pin piston is moved toward the primary charge, the piercing pinpunctures the closure disc before the firing pin engages the percussionprimer.
 6. The firing mechanism of claim 1, wherein the piercing pin hasa barbed tip.
 7. The firing mechanism of claim 1, wherein the piercingpin is threadably coupled to the piston body.
 8. The firing mechanism ofclaim 1, wherein the percussion primer is a first percussion primer andthe firing pin is a first firing pin, the firing pin assembly furtherincluding a second percussion primer, the firing pin piston having asecond firing pin extending from the piston body, such that when thefiring pin piston is moved toward the primary charge the second firingpin engages the second percussion primer.
 9. The firing mechanism ofclaim 8, wherein the housing defines a first lower channel, a secondlower channel, and a central pin channel, the first percussion primerdisposed in the first lower channel, the second percussion primerdisposed in the second lower channel, and the piercing pin disposed inthe central pin channel, wherein the central pin channel is parallel toand between the first and second lower channels.
 10. The firingmechanism of claim 1, wherein the firing mechanism does not include anignition charge between the percussion primer and the primary charge.11. A pyrotechnic device comprising: a body defining a chamber; a pistondisposed in the chamber; and a firing mechanism coupled to the body, thefiring mechanism to, when triggered, generate high pressure in thechamber to move the piston, the firing mechanism including: a housingdefining a first bore, a second bore, and a channel between the firstbore and the second bore; a firing pin assembly disposed in the firstbore; a primary charge disposed in the second bore; and first and secondclosure discs welded to the housing to hermetically seal the primarycharge in the second bore.
 12. The pyrotechnic device of claim 11,wherein the first closure disc is welded to an inner surface of thehousing defining the second bore.
 13. The pyrotechnic device of claim12, wherein the second closure disc is welded to an end of the housingover the second bore.
 14. The pyrotechnic device of claim 11, whereinthe firing pin assembly includes a firing pin piston including apiercing pin to puncture the first closure disc when the firing pinpiston is moved toward the primary charge.
 15. The pyrotechnic device ofclaim 14, wherein the piercing pin has a barbed tip.
 16. The pyrotechnicdevice of claim 14, wherein the firing pin piston includes a pistonbody, the piercing pin coupled to and extending from the piston body.17. The pyrotechnic device of claim 16, wherein the firing pin assemblyincludes a percussion primer, and wherein the firing pin piston includesa firing pin extending from the piston body, the firing pin to engagethe percussion primer when the firing pin piston is moved toward theprimary charge.
 18. An aircraft comprising: a forward fuselage defininga cockpit; a canopy removably coupled to the forward fuselage over thecockpit; and a pyrotechnic device to unlatch the canopy from the forwardfuselage, the pyrotechnic device including a firing mechanism, thefiring mechanism including: a housing defining a first bore, a secondbore, and a channel between the first bore and the second bore; aprimary charge disposed in the second bore; a closure disc between thesecond bore and the channel; a percussion primer; and a firing pinpiston including a piston body, a firing pin extending from the pistonbody, and a piercing pin extending from the piston body, the firing pinbeing a first distance from the percussion primer and the piercing pinbeing a second distance from the closure disc, the second distance beingless than the first distance.
 19. The aircraft of claim 18, wherein theclosure disc is welded to the housing.
 20. The aircraft of claim 18,wherein the piercing pin has a barbed tip.